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SN74AXC8T245: Max protocol speed undergoing board level shift

D Jain
Prodigy 20 points

Part Number: SN74AXC8T245
Other Parts Discussed in Thread: TXV0108

Hi,

 

For our next gen SoC product (in the market in 1+years), I am looking for a component which can help do a board level voltage level conversion between 1.2V <-> 1.8V for interfaces like RGMII at 125Mhz or OSPI DDR at 200Mhz. The high level issue is that in advanced technologies, it is easier to support 1.2V IO than 1.8V IO.

 

  1. I was looking at SN74AXC8T245 from TI: the data sheet says “Up to 380Mbps support when translating from 1.8V to 3.3V”. What is the data speed from 1.2V to 1.8V and 1.8V to 1.2V? Does 380mbps for 8 bits means that a single bit can only be translated at a max of 47.5mhz?
    1. Do you see any speed impact (or any impact for that matter) for a protocol with bi-direction signals (going from master -> slave and slave -> master in a single clock) translating between 1.2V & 1.8V or is the max speed only able to hit for a protocol in which all the signals go in a single direction (master -> slave or slave -> master) on one clock?
  2. Can you suggest if TI may have some other part which is more suited to my needs and the rough retail cost for that part?

 

Thanks for your inputs!

  • 0
    TI__Mastermind 36010 points

    Hello D Jain,

    Getting 125MHz when operating at 1.2V <-> 1.8V is pretty difficult to achieve. 

    If you use the following formula (1/tpd), we can estimate the max data rate which will be 111Mbps or 55MHz at 1.2V -> 1.8V.

    We have another part, TXV0108, that's designed for RGMII. Similar to the AXC, however, it has limited RGMII support at 1.2V.

    Regards,

    Josh